Referring to FIG. 1, an exemplary hydraulic system 10 having fittings, piping, and equipment is schematically illustrated. In one example, the hydraulic system 10 can be a relief system, such as used for a flare stack in a chemical plant. Thus, the present example of the hydraulic system 10 has pressure vessels 12, relief valves 16, a knockout drum 13, and an elevated flare stack 18 interconnected by piping 14 and junctions 15. The relief valves 16 discharge overpressure from the vessels 12 to the knockout drum 13 and elevated flare stack 18 in the event of an overpressure contingency. Of course, such systems 10 are typically more complex than illustrated in the example of FIG. 1 and will have a number of elements which are not shown but which would be present to circuit the piping 14 in an actual implementation.
During a hydraulic analysis, a user performs hydraulic calculations to determine pressure drops, flow rates, or other hydraulic parameters that may occur in the system 10 under various conditions. As a first step in the analysis process, a user typically starts with an isometric drawing or blueprints of the system 10 to be analyzed, and inputs that system into a software application to provide further details relevant to modeling the system that may not be reflected in the isometric drawings alone. Such an isometric drawing is typically created with a three-dimensional (3-D) drawing program, such as AutoCAD, and information from the isometric drawing is usually entered into the software application by a user by hand, although the start drawing could also be conceivably be loaded into the software application even if it lacks some information pertinent to the subsequent modeling of the system.
In particular, 3-D information concerning the size and orientation of piping, fitting, equipment, etc. is entered into the software application because such information is important to accurately model the hydraulics. Additionally, information concerning the expected hydraulic operation and limits of the various elements is entered into the software application, and to the extent that a particular element has already been modeled and entered into the software application, it can be retrieved from a library of elements. For example, information concerning the trip pressure for a relief valve 16 would be entered into the software application, and/or would already be stored in the application for ready retrieval by a user.
Various software applications of the type described above for creating a model of a system 10 are known in the art, such as Visual Flow™, Flare Net, and Tri-Header, which are all incorporated by reference herein. Another software application is Pressure Protection Manager™ by Berwanger, Inc. disclosed in U.S. Pat. No. 5,774,372, which is incorporated herein by reference.
To create the model for performing the hydraulic calculations in the software application, the system 10 is divided into primary elements of segments and node points. Using a node-segment convention known in the art for hydraulic calculations, node points (e.g., N1 to N7 in FIG. 1) are defined at particular elements in the process, and segments are defined as the collection of fittings (not shown) and piping 14 between the node points. The elements where node points are defined conventionally include sources (e.g., relief valves 16), outlets (e.g., elevated flare tip 18), junctions (e.g., tees 15), or pieces of network equipment (e.g., knockout drum 13).
Defining node points at these elements in the system 10 is required for performing the hydraulic calculations. For example, a junction 15 must be defined as a node point because the hydraulic calculations must resolve the mass flow rates and other variables occurring at the three openings of the junction 15. Similarly, sources and outlets must be defined as node points of the system 10 because the mass flow rates from all the sources must equal the mass flow rates to all the outlets. In addition, equipment, such as a relief valve, is conventionally defined as a node point because the fluid dynamics of such equipment can be complex and the equipment's characteristics for the hydraulic calculations are approximated. It may also be beneficial to define changes in orifice dimension, such as changes in pipe diameter or ANSI expansions, as node points.
Some prior art software applications require the user to create a model of the hydraulic system by manually entering information concerning node points (sources, outlets, equipment, and junctions) and segments (piping and fittings) into a tabular form. Because a hydraulic system can have hundreds of pieces of equipment, pipe lengths, fittings, etc., entering the information manually in tabular form is time consuming and prone to errors. To overcome these difficulties, prior art software applications such as those mentioned above allow a user to visually construct a model of the hydraulic system instead of using mere tables. Referring to FIGS. 2A-2B, interfaces 20 and 40 of a prior art software application, Visual Flow™ (also known as Visual Flare) by SimSci-Esscor, are illustrated. Using the first interface 20 of FIG. 2A, the user constructs a two-dimensional (2-D) system model 30 of the hydraulic system. Then, using the second interface 40 of FIG. 2B, the user constructs 3-D segment models of the segments of the hydraulic system.
In FIG. 2A, the first interface 20 includes a pallet 22 for constructing the 2-D system model 30 using tools 24 on a toolbar. The node-segment convention discussed above is used to construct the 2-D system model 30. Thus, node points are defined at conventional elements (e.g., sources 32, outlets 33, equipment 34, and junctions 36). In addition, segments (e.g., line 38) interconnect the node points and represent the piping and fittings of the system.
The tools 24 include buttons for adding nodes or segment to the pallet 22. To add a node element (e.g., source 32, valve 34, outlet 33, or junction 36), the user selects the desired node tool 25 and clicks on a location of the pallet 22 to add the node element. A dialog box (not shown) then allows the user to define aspects of the element, such as tag numbers, flow rates, pressures, etc., or again such information may already be populated in an element library and automatically retrieved. To add segments between node points, the user selects the segment tool 27 and connects the node points on the pallet 22 with an interconnecting line 38, which merely represents the connection between the node points and which (at this point) lacks any details on the piping and fittings used or their orientations. In this prior art software application, the user does not define node points at changes in orifice dimensions, expansions, contractions, or changes in pipe diameters, and thus a given segment can include such features.
Once the 2-D system model 30 has been created, the user double clicks on a segment (e.g., line 38 in FIG. 2A) to bring the user to the second interface 40 of FIG. 2B. In this interface 40, the user constructs a 3-D segment model 46 of the segment, which, in short, allows the user to portray the actual physical layout of the segment in question (i.e., does it travel up or down, left or right, what sorts of fitting or elbows are used, etc.). The second interface 40 includes a pallet 42 for visually constructing the segment and includes tools 44 for selecting piping sizes and fitting types. After selecting a piping size, the user clicks at a starting point on the pallet 42 with the mouse pointer 41, and the starting node point (e.g., junction 36) of the selected segment is then displayed on the pallet 42. Using this 3-D view, the user moves the mouse pointer 41 in the required direction for the piping, which is represented by line 48 on the pallet 42. As the user moves the mouse pointer 41, a length dimension (not shown) is displayed adjacent the line 48 to indicate the length of piping being drawn. After moving the desired direction and length, the user clicks on the pallet 42, and a selected fitting 47 from the tools 44 is inserted at that location. The user repeats the above drawing steps until the user reaches the end of the segment and double clicks on the pallet 42 to enter the ending node point (e.g., outlet 33).
After constructing the 3-D segment model 46 for the selected segment, the user returns to the 2-D system model 30 in FIG. 2A. Another segment can thereafter be selected in the 2-D interface 20 of FIG. 2A to access the second interface 40 of FIG. 2B and to construct or view a 3-D segment model of the newly selected segment.
When the required piping lengths and fittings have been entered for all the segments of the hydraulic system into the software application, the user accesses a hydraulic solver in the software application to perform hydraulic calculations and modeling based upon the inputted 3-D data and other relevant hydraulic data present in the model (e.g., relief valve trip pressures, etc.). The algorithms used by hydraulic solvers are well known in the art, such as Beggs, Brill and Moody; Moody; Beggs and Brill high velocity; and Lockhart and Martinelli, Berwanger NetMaster 1.0, for example, but which are incorporated herein by reference. The hydraulic solvers allow a user to determine the performance of the hydraulic system during a specific global scenario or common contingency, such as a fire. By inputting the scenario, the flow rates, fluid properties at all sources, pressures at the outlets, and other required conditions and information into the hydraulic solver, the solver can determine (for example) backpressure results, which the user can then use to determine whether the backpressures will cause a catastrophic failure, for example. As hydraulic solvers are well known, they are not further discussed.
One disadvantage of this prior art software application is that the user is unable to split a segment into two segments from the second interface 40. For example, if the user realizes that a node point (e.g., a junction) should have been located somewhere in the segment (e.g., on line 48 in FIG. 2B), the user must exit the 3-D interface 40, return to the 2-D interface 30 to add the node point to the segment (e.g., line 38), and return to the 3-D interface 40 to reenter segment information. In another disadvantage, the user may find it difficult to move the mouse pointer 41 to draw the precise length of piping. Consequently, the user may simply approximate piping lengths while constructing the segment with the mouse pointer 41 and may use a dialog window (not shown) to manually enter the actual piping lengths for the segment.
Perhaps more importantly, constructing a 3-D segment model 46 of FIG. 2B for each segment of a hydraulic system can still produce errors in the entire system model, and accordingly can produce errors in the hydraulic calculations based on such an erroneous model. For example, when constructing a 3-D segment model 46 for a given segment, the user is not provided feedback whether the pipe lengths, 3-D orientations, etc. are physically accurate in light of the entirety of the hydraulic system. This is because the user can only view one 3-D segment model 46 at a time in the second interface 40 of FIG. 2B, and cannot view two or more adjoining 3-D segment models 46 together in a 3-D context. The only other avenue for viewing the entirety of the hydraulic system, or multiple segments, is provided by the 2-D interface of FIG. 2A, which (like a typical circuit schematic) indicates the positions and lengths of the segments in only a functional, non-physical manner. Therefore, it is possible for the user to produce unrecognized errors which respect to the 3-D layouts of the segments. For example, a portion of one segment may inadvertently occupy the same physical location as another segment. For example, valve 34 in FIG. 2A (segment 39) may occupy the same 3-D space as the outlet 33 (segment 38) because the user has entered an incorrect pipe length or orientation in one of the segments 38 or 39. This might never be noticed by the user, and as a result any calculations performed using the 3-D modeling information, which necessarily relies on the 3-D data from input for each of the segments, would likely be incorrect.
Without the ability to view the 3-D system model of the entire hydraulic system (or at least two adjoining 3-D segment models), the user is offered no visual feedback of such an error. Having two elements occupy the same space is not physically possible, and any hydraulic calculations performed on an incorrect model will produce erroneous results as just noted. Therefore, a need exists in the art of hydraulic modeling for a software application that allows a user to construct a model efficiently, and in a manner that reduces errors such as those just noted. The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.